This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The purpose of this study has been to examine how the aging process differentially affects females of three closely related primate species: the human, the chimpanzee, and the rhesus monkey. This evolutionary process has led to unique characteristics of the aging phenotype of the human, which can be best understood by comparing brain and cognitive aging in the human with the same features in our closest relative, the chimpanzee, and in the most widely studied biomedical model of human aging, the rhesus monkey. Using comparable measures in these three species and employing both cross-sectional and longitudinal studies, we developed a comprehensive and integrated overview of social, cognitive, and neural aging in these three closely related Old World primates. During the reporting period, we conducted a series of behavioral tests on the monkeys and chimpanzees, including tests of learning and memory and performed a test of socio-emotional cognition on chimpanzees. We have measured age-related cognitive function in humans, using the same tests we employed in the nonhuman primates. Our lab carried out MR scans designed to examine brain white matter in the three species. The data will provide new insights into the neural basis of age-related cognitive decline and into the factors that govern successful versus unsuccessful aging. This comparative analysis of human and nonhuman primates should also help explain why humans develop such age-related disorders as Alzheimer's disease, while monkeys and apes do not.